Perforated arc chute barrier with arc constricting slot



Nov. 22, 1955 J. w. TIMMERMAN PERFORATED ARC CHUTE BARRIER WITH ARC CONSTRICTING SLOT Filed Feb. 3, 1951 5 W Z 5 A m Ilu C O U U \1 o m 4. k 0 n @Qo a p o 5 4 4d "a w F J u 5 3 v 1 en 6 00 M q 4 r 1 I I I l I I I I I IM W \u\ o 0 O 0 H U Q g o o o o o o w 4 6 v 6 6 2 2 .v ,n n 0 2 I, /-O H 2 f. n Z 3 5 o o 0 7 n1 n C 6 O O O O Q g 2 Q a 5 2 2 7 2 M O O O O o O U 0 0 a 2 United fitates PERFORATED ARC CHUTE liARRllER WITH ARC CONSTRKCTING SLQT Julius W. Timmerman, Waukesha, Wis., assignor to utilis- Chalmers Manufacturing Company, Miiwaukee, Wis.

Application February 3, 1951, Seriai No. 209,3il2

Claims. (Cl. ace-nan This invention relates in general to circuit interrupting devices and more particularly to are extinguishing means forming a part thereof.

In the construction and operation of circuit interrupters, it is frequently necessary to provide means for extinguishing quickly the are which is drawn between separable arcing contacts. This are is usually blown by blowout means, such as a magnetic blowout coil or an air blast, into an arc chute which is arranged to quench the are by lengthening it, cooling it, or a combination of both.

Arc chutes having spaced insulating plates to lengthen the arc or squeeze the are into narrow slots have been used to rapidly increase the arc resistance, decrease the arc current and greatly improve the power factor, thereby facilitating interruption of the are at a current zero. However, it has been found in many cases that the arc moves rapidly through the arc chute and the highly heated arc gases expelled from the chute form a conducting path at the chute exhaust through which the arc may restrike after it has been interrupted within the chute. Such restriking or flashover at the chute exhaust usually results in failure of the circuit breaker to clear the circuit and damage to other equipment associated therewith.

In accordance with the invention claimed an arc chute is provided adjacent a pair of arcing contacts for receiving the are at one end thereof and exhausting the arcing products at the other end thereof. The are chute employs an arc extinguishing device comprising a plurality of slotted spaced insulating plates arranged to extend longitudinally of the axis of the arc chute with the slots adjacent the arcing contacts to form an arc passage. Each of the plates is provided with a plurality of apertures which may be arranged to extend in a straight line extending from the slot of each plate toward at corner of the plate near the exhaust end of the chute for providing auxiliary arc passages which rapidly cool and extinguish the arc. The sizes of the apertures in each plate may gradually decrease in diameter from the slot to the corner of the plate at the exhaust end of the chute and the lines of apertures in adjacent plates may diverge to adjacent corners of the respective plates, thereby providing a zigzag path which restricts and lengthens the arc in the direction of are movement. The slots of the barrier plates are arranged to gradually restrict the cross section of the arc in a direction normal to the direction of arc movement to the size of the apertures nearest the slot. In this manner the slot constricts the are before the arc is moved through the apertures.

It is, therefore, one object of the present invention to provide a new and improved arc interrupting device in which the arc is constricted in a predetermined manner as it passes through an arc chute.

Another object of this invention is to provide a new and improved arc extinguishing device in which the arc 2,724,754 Patented Nov. 22, 1955 ice is gradually restricted to a predetermined cross section as it passes through a given are path and is further restricted and lengthened as it passes through a plurality of auxiliary arc passages.

A further object of this invention is to provide a new and improved arc extinguishing device in which the arc is constricted in a predetermined manner before it is driven through a plurality of zigzag passages which rapidly lengthen, cool and extinguish the arc.

Objects and advantages other than those above set forth will be apparent from the following description when read in connection with the accompanying drawing, in which:

Fig. 1 is a view in cross section, of a magnetic blowout type circuit breaker employing the present invention;

Fig. 2 is an enlarged view of one of the barrier plates illustrated in Fig. 1;

Fig. 3 is an enlarged view of the stack of barrier plates shown in Fig. 1 wherein one are barrier plate is made as illustrated in Fig. 2 and the alternate barrier plate is a modification thereof; and

Figs. 4 and 5 are views of other modifications of the stacks of barrier plates of the arc chute illustrated in Fig. 1.

Referring more particularly to the drawing by characters of reference, Fig. 1 illustrates a magnetic blowout type of circuit breaker including as elements thereof a pair of terminal studs 6 and 7 for connecting the circuit breaker to line conductors (not shown). Although, in general, circuit breakers of the type considered in Fig. l are provided with a plurality of similar pole structures, one for each phase of a polyphase electric circuit, only one such pole structure is shown in the drawing and the circuit breaker will be described in detail as if it was of the single pole unit type.

The circuit interrupter or breaker in Fig. 1 comprises essentially means for opening the circuit to form the interrupting arc and an arc extinguishing structure. Specifically, the circuit opening means comprises a fixed current carrying contact 8, a fixed tertiary contact 9, a fixed arcing contact 10, and a movable arcing contact 11. Arcing contact 11 is mounted on a lever 28 which is pivotally mounted at 12 on an extension 13 of the circuit breaker stud 6 and is operated by means of a reciprocally movable rod 14. The operating rod 14 is suitably connected to an actuating mechanism (not shown) for operating the movable contact between closed and open circuit positions. Fig. 1 illustrates the movable contact 11 in an intermediate position. The arcing contacts are electrically connected to the lower ends of terminal studs 6 and 7. Accordingly, when the breaker is connected in series in a power circuit and the arcing contacts are separated, an arc may form therebetween across the gap indicated.

For the purpose of interrupting this power are, an arc extinguishing structure, such as an arc chute 15, may be mounted so as to receive the power are which is under the influence of a magnetic blowout means. The are chute preferably is disposed directly above the arcing contacts, as shown, when the blowout means act upward, but may be mounted in any other suitable location when the blowout means act in other directions. The switch or arcing contacts and the magnetic blowout structure can assume any preferred form so that a brief description thereof will be sufiicient. The magnetic blowout means may comprise a core 17, poles 18, and a coil 16 which is electrically connected to the terminal stud 7 and to a metallic arc runner 19 so that the arc current (as the arc travels along the runner) flows through the blowout coil in a manner well known in the art.

Normally the current is carried in the closed circuit position of the breaker by contact 11 and the spring biased contact 8. As the movable arcing contact 11 is actuated toward open circuit position, current is shunted from fixed contact 8 first to fixed contact 9 and then to fixed arcing contact 10. As the arc is drawn by the movable arcing contact 11, the arc terminal on arcing contact 10 is transferred to are runner 19, which is usually an extension arm of the fixed arcing contact 10. As the movable arcing contact 11 reaches its full opening stroke, the other arc terminal transfers from the movable arcing contact 11 to an arc runner 20 which directs the are into the arc chute 15. The arcing contact 10 and the arc runner 19 are electrically connected in series with the blowout coil 16 and stud 7. Accordingly, the blowout coil is already energized at the inception of the arc interruption to influence the arc in a Well known manner, i. e., to drive it into the arc chute in an expanding loop. It will be apparent to one skilled in the art that the blowout field can be utilized in the most efiicient manner by disposing the iron poles 13 so as to cooperate with the blowout coil in the conventional manner outside of the arc chute.

In accordance with the invention claimed, arc chute 15 is provided with a plurality of slotted spaced insulating plates 25 arranged to extend longitudinally of the axis of arc chute 15 with the slots adjacent the arcing contacts forming an arc passage 26. Each plate 25 is provided with a plurality of apertures 27 which may, for example, extend in a. straight line extending from the area immediately adjacent the slots of each plate 25 toward a corner of plates 25 located near the exhaust end of arc chute 15. The apertures in each plate, as illustrated in Figs. 2 and 3, may gradually decrease in diameter from the slot to the corner of each plate located in the exhaust end of arc chute 15. The lines of apertures in adjacent plates 25 may diverge to adjacent corners thereof. Each of said apertures in adjacent plates forming particular are passages may be inequally spaced from the arc passage 26, thereby forming a zigzag path through each row of apertures.

Under normal interrupting conditions an arc is initiated immediately upon separation of the arcing contacts 10 and 11. The terminal of the are on fixed arcing contact 10 is driven over arc runner 19 by the magnetic blowout means and the thermal elfect of the are. As movable arcing contact 11 nears its fully open position the other terminal of the arc jumps from contact 11 to are runner 20 and is also driven by the blowout means and the thermal etfect of the arc toward the exhaust end of arc chute 15 As the arc terminals move along the arc runners 19 and 20 toward the exhaust end of arc chute 15 the arc is driven into passage 26 formed by the slots of plates 25.

The are rises in passage 26 under the influence of the blowout means and the thermal efiect of the arc until it is constricted at the closed U-shaped slot end. As the arc moves through passage 26 it is restricted by the sides of the slot and constricted to a predetermined size in a direction normal to the direction of arc movement. The slots forming passage 26 each comprise a wide mouth V-shaped portion arranged adjacent the arcing contacts for gradually restricting the arc to a predetermined size and a narrow elongated U-shaped portion arranged adjacent the largest aperture in each plate for retaining the arcs restricted size during its movement through the second portion of the slot. This predetermined size may, for example, be equal to the diameter of the apertures nearest the slot which form the first auxiliary arc passage. By constricting the arc during its passage through the slots of the barrier plates to approximately the diameter of the apertures which form the first auxiliary arc passage located nearest the slots, the arc may move from passage 26 to the first auxiliary arc passage with relative ease and without overheating the closed slot end of the barrier plates. This feature is important because it per mits the arc to rapidly reach that portion of the arc chute where it may be most effectively elongated, cooled and rapidly extinguished.

As the arc moves through the plurality of relatively cool auxiliary arc passages, it is further restricted in diameter by the apertures, and the arc section extending between adjacent barrier plates spread around the apertures and are cooled by the surface action of plates 25. Each arc path in the sequence extending from the passage 26 to the apertures arranged near the exhaust end of the arc chute constricts the diameter of the are a little more than the preceding are path, thus cooling the arc by subjecting it to a larger surface area and increasing the voltage gradient of the arc to expedite rapid arc extinction.

By arranging the lines of apertures in adjacent plates so that they extend from the slot toward adjacent corners or" the barrier plates 25, a zigzag path is provided through each row of apertures which restricts and lengthens the arc in the direction of arc movement. The apertures also retard the movement of the arc through the arc chute so that the arc may be exposed to the cooling surfaces of the arc chute for a longer period of time than heretofore provided.

Fig. 4 illustrates a barrier plate having a slot similar to the slot of the barrier plates of Figs. 2 and 3 but having a V-shaped slot end. This V-shaped slot end further constricts the are before it enters the auxiliary passages formed by the apertures and provides an easier progression of the are up and over the webs which separate the slots from the apertures.

Fig. 5 illustrates a V-shaped notch slot in the barrier plates, which slot gradually constricts the are along the full length of arc passage 26. This type of slot constricts the arc to a size which is smaller than the size of the apertures in the auxiliary arc passage nearest passage 26.

Arc chute structures of the type illustrated in Figs. 1 to 5 may be used for interrupting direct current circuits as well as alternating current circuits. In direct current circuit interruptions, the arc formed in the slotted passage spreads around the closed end of the slots and is cooled by the surface action of the barrier plates. As the arc spreads around the closed end of the slots, the air in the row of apertures nearest the slots becomes ionized and an arc section in parallel with the original arc strikes through the arc path formed by these apertures. This arc section increases in size until the original arc becomes unstable and is extinguished. This same sequence of events happens again within the arc path formed by apertures of each plate located downstream of the former are path. This step by step movement of the are through the arc chute continues, bringing the are into contact with more and more cooling surface until the arc is extinguished.

Although but a few embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. An electric circuit interrupter comprising arcing contacts and an arc chute for receiving and extinguishing the arc, said chute comprising a plurality of slotted spaced insulating plates arranged to extend longitudinally of the axis of said chute with the slots adjacent said arcing contacts to form an arc passage, a number of said plates being provided with a plurality of apertures extending in a straight line from said slots toward the exhaust end of said chute for providing a plurality of auxiliary arc passages, said slots comprising first portions arranged adjacent said arcing contacts for gradually restricting the arc to the size of the largest apertures and narrow elongated substantially constant width second portions adjacent said apertures for retaining the arcs restricted size during its movement through the second portion of said slots.

2. An electric circuit interrupter comprising arcing contacts and an arc chute for receiving and extinguishing the arc, said chute comprising a plurality of slotted spaced insulating plates arranged to extend longitudinally of the axis of said chute with the slots adjacent said arcing contacts to form an arc passage, a number of said plates being provided with a plurality of apertures extending in a straight line from said slots toward the exhaust end of said chute for providing a plurality of auxiliary arc passages, said slots comprising first V-shaped portions arranged adjacent said arcing contacts for gradually restricting the arc to the size of the largest apertures and narrow elongated U-shaped portions arranged adjacent said apertures for retaining the arcs restricted size during its movement through the second portions of said slots.

3. An electric circuit interrupter comprising arcing contacts and an arc chute for receiving and extinguishing the are, said chute comprising a plurality of slotted spaced insulating plates arranged to extend longitudinally of the axis of said chute with the slots adjacent said arcing contacts to form an arc passage, a number of said plates being provided with a plurality of apertures extending in a straight line from said slots toward the exhaust end of said chute for providing a plurality of auxiliary arc passages, said slots comprising aligned wide mouth V- shaped portions arranged adjacent said arcing contacts for gradually restricting the arc to the size of the largest apertures and aligned parallel sided V-pointed portions arranged adjacent said apertures for retaining the arcs restricted size during its movement through the second portions of said slots.

4. An electric circuit interrupter comprising arcing contacts and an arc chute for receiving and extinguishing the are, said chute comprising a plurality of slotted spaced insulating plates arranged to extend longitudinally of the axis of said chute with the slots arranged adjacent the arcing contacts to form an arc passage, each one of said plates being provided with a plurality of apertures arranged in lines diverging from the slot toward one of the corners of the plate near the exhaust end of said chute for providing a plurality of secondary arc passages, said slots comprising first portions for gradually restricting the arc in a direction normal to the direction of arc movement to a predetermined size and narrow elongated substantially constant width second portions adjacent said apertures for retaining the arcs restricted size during its movement through the second portion of said slots, the lines of apertures in adjacent plates diverging to opposite corners of the respective plates near the exhaust end of said chute to provide a zigzag path which further restricts and lengthens the arc in the direction of arc movement.

5. An electric circuit interrupter comprising arcing contacts and an arc chute for receiving and extinguishing the arc, said chute comprising a plurality of slotted spaced insulating plates arranged to extend longitudinally of the axis of said chute with the slots arranged adjacent the arcing contacts to form an arc passage, each one of said plates being provided with a plurality of apertures arranged in lines diverging from the slot toward one of the corners of the plate near the exhaust end of said chute for providing a plurality of auxiliary arc passages, each slot comprising a wide mouth V-shaped portion arranged adjacent said arcing contacts for gradually restricting the arc to the size of the largest aperture in said plate and a narrow elongated U-shaped portion arranged adjacent said largest aperture for retaining the arcs restricted size during its movement through the second portion of said slot.

References Cited in the file of this patent UNITED STATES PATENTS 1,840,292 Slepian I an. 5, 1932 1,868,442 Corbett July 19, 1932 2,140,360 Jennings Dec. 13, 1938 2,147,430 Ellis et al Feb. 14, 1939 2,244,061 Graves, Jr. June 3, 1941 2,442,199 Dickinson et al. May 25, 1948 2,468,422 Wood Apr. 26, 1949 2,616,006 Frink Oct. 28, 1952 FOREIGN PATENTS 332,484 Italy Nov. 30, 1935 615,025 Great Britain Dec. 31, 1948 

